Some existing positioning systems such as global positioning systems (GPS) determine the location of devices using satellites. Other systems such as collaborative positioning systems determine the location of the devices based on crowd-sourced data. The crowd-sourced data typically includes a list of beacons observed at a particular location along with identification of the particular location as obtained by mobile devices such as laptops, netbooks, and cellular telephones. The positions of the beacons are then used to estimate the location of devices (e.g., those lacking GPS capability or coverage) that request position information based on an observed list of beacons. The complexity and accuracy of the estimations depend in part on which beacons are selected for the estimations.